The invention concerns a method and an apparatus for the detection of defective track wheels on rail vehicles such as locomotives and railway carriages.
With hitherto-known methods, the checking of whether the wheels are defective is carried out while the vehicles are standing still. Among other things it is thus known to use ultrasound measurements and electromagnetic eddy current measurements when the carriages are at a standstill. Moreover, it is commonly known to carry out purely manual detection, in that a hammer or the like is used to tap the wheels one after the other, whereby the practised test person purely from experience can thus hear whether a wheel is defective from the ringing tone from the wheels.
The object of the invention is to provide a method and an apparatus whereby it can be detected with greater certainty than with known techniques and while the wheels are rolling whether a wheel is defective, i.e. while the locomotives and the carriages are running in the normal manner.
This is achieved by a method whereby, while the locomotive and/or the carriage is running, an electromagnetic beam is directed towards the wheel in a direction substantially at right-angles to the plane of the wheel, that a series of signals are detected corresponding to the reflected electromagnetic beams from the wheel substantially at right-angles to the plane of the wheel, that a measurement is effected of the Doppler frequency change between the transmitted beam and the reflected beam, that on the basis of this a signal processing is effected to determine the vibration pattern of the relevant wheel, and that a determination of the condition of the relevant wheel is undertaken on the basis of the vibration pattern.
The invention also concerns an apparatus which is characteristic in that it comprises a laser sensor for the measurement of the speed of lateral vibrations of a wheel, in that the laser sensor is designed to transmit a laser beam towards the wheel in a direction substantially at right-angles to the plane of the wheel, that the laser sensor is designed to receive beams reflected from the wheel, and that the laser sensor is designed to calculate the substantially lateral vibrations of the wheel on the basis of the Doppler frequency change, that the apparatus comprises elements to determine a vibration pattern for the individual wheels on the basis of the calculated lateral vibrations of a number of points on the individual wheel, and that the apparatus comprises memory units for the storage of the measured data.
With the method respectively the apparatus according to the invention, it is thus achieved that detection of the individual rail vehicles, locomotives, carriages etc. can be carried out while these are running in a normal manner on the railway tracks, in that one or more places on particularly busy railway sections can be selected on which measurements are under-taken according to the invention. There will thus be achieved a greater degree of security against accidents arising from defective wheels, and greater operational security will also be achieved, in that possible future defects will be able to be detected in such good time that a replacement or repair will be able to be planned.
With the invention, one or more laser sensors or the like are placed in the vicinity of a rail element on which the carriages and the locomotives operate, so that the transmitted laser beam is transmitted towards and substantially at right-angles to the plane of the wheels, and such that a suitable part of the wheel disk is swept by the laser beam. For example, the laser sensor can be placed so that the beam impinges on the wheel disk mainly between the wheel axle and the rim of the wheel.
The laser sensor will thus be able to measure the speed of the wheel""s lateral vibrations. These vibrations, which are caused by the physical influences on the wheel, will contain information concerning the condition of the relevant wheel, corresponding to that information which is obtained by the tapping of a static wheel and subsequent evaluation of the ringing tone from the wheel.
Since the laser sensor with its associated equipment is set up in a permanent position, special measures can be taken in order to ensure that the wheels vibrate to a sufficient degree or in a special manner to enable sufficiently good measuring results to be achieved. There can thus be irregularities in the track itself, or a device can be provided whereby during the passage of the wheel this abuts against a part of the wheel, such as e.g. the wheel flange.
When the laser sensor has detected the reflected signals, a subsequent processing of the signals is effected with the object of producing signals which are representative of the wheel""s vibrations, and a storage of all the measured signals is carried out.
With the method and the apparatus, an appropriate measurement is effected which ensures an identification of the wheels and/or the carriages/locomotives on which the detection is being carried out. For example, the carriages/locomotives and/or the individual wheels can be provided with known types of identification markers which can be detected and identified by contact-free measurements, such as e.g. magnetic, inductive, capacitive or optical identification markers. Therefore, the apparatus according to the invention should preferably also comprise elements for the identification of these identity markers, and a subsequent storage of this data is effected in such a manner that the correlation with the vibrations measured from the relevant wheels is ensured.
A suitably large number of measurements are carried out for each wheel, hereby ensuring that the vibration pattern of the relevant wheel is determined to a sufficient degree. A further signal processing can then be carried out with the object of determining whether the individual wheel is defective or in order. This can be carried out e.g. by comparing the vibration pattern with representative vibration patterns, where a deviation (within certain tolerances) can result in the relevant wheel being judged to be defective. An evaluation can possibly result in a message being sent to a central surveillance unit to the effect that the relevant wheel must be given a closer examination, e.g. by an examination of the types known in the introduction, when the relevant carriage or the relevant locomotive is available at a station or in an engine shed where the examination can take place.
The further signal processing can also take place by comparing the measurements obtained from a wheel with earlier measurements from the same wheel or possibly from wheels which are of the same type as the relevant wheel, which will be the case if the wheels used are divided into categories, where wheels within the same category have identical or more or less the same vibration patterns. If during this comparison the relevant wheel displays unacceptable deviation, it can thus be judged to be defect or possibly, as mentioned above, it can be pointed out as a wheel which must be subject to further investigation. In both cases a message to this effect will be sent from the apparatus to a central surveillance unit.
The recorded measurements, especially including the measured vibration patters, can be collected in a database where they can be used for carrying out various analyses, and can serve to improve future diagnoses. For example, the database can be used to form a picture of the temporal development of the vibration pattern for specific wheels throughout their lifetimes, and the general development of the vibration patterns over periods of time can also be followed.